CODEWITHSUNDEEP
c++destructor
Tom S
Tom S

Reputation: 551

Destruction order in C++

#include <iostream>
class X{
public:
    X(int n = 0) : n(n) {}
    ~X() {std::cout << n;}
    int n;
};
void main()
{
    X a(1);
    const X b(2);
    static X c(3);
}

Output is 213, I thought the destructor uses a LIPO stack, so why it doesn't destruct in a reverse order 321?

I'm pretty confused and I'd like to know more about it. Thank you so much.

Upvotes: 0

Views: 358

Answers (3)

ShadowRanger
ShadowRanger

Reputation: 155403

That is LIFO. a and b are destructed in reverse order when main returns, c is destructed at some undetermined point between when main returns and the program actually exits (because it's static, tied to the lifetime of the program, not main itself).

Upvotes: 1

Kiskae
Kiskae

Reputation: 25573

It is calling the destructors in reverse order, but a static variable has a different lifetime.

See Does C++ call destructors for global and class static variables? which explains that variables with a global lifetime are destructed sometime after main returns.

Upvotes: 1

Igor Tandetnik
Igor Tandetnik

Reputation: 52471

a and b are of automatic duration, destroyed when the block ends. c is of static duration, destroyed when the program terminates. LIFO order only applies to objects destroyed at the same point in the program.

Upvotes: 3

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